const autoprefixer = require('autoprefixer');
const path = require('path');
const webpack = require('webpack');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const CaseSensitivePathsPlugin = require('case-sensitive-paths-webpack-plugin');
const InterpolateHtmlPlugin = require('react-dev-utils/InterpolateHtmlPlugin');
const WatchMissingNodeModulesPlugin = require('react-dev-utils/WatchMissingNodeModulesPlugin');
const eslintFormatter = require('react-dev-utils/eslintFormatter');
const getClientEnvironment = require('./env');
const paths = require('./paths');

//Webpack uses `publicPath` to determine where the app is being served from.
//In development, we always serve from the root. This makes config easier.
const publicPath = '/';
//`publicUrl` is just like `publicPath`, but we will provide it to our app
//as %PUBLIC_URL% in `index.html` and `process.env.PUBLIC_URL` in JavaScript.
//Omit trailing slash as %PUBLIC_PATH%/xyz looks better than %PUBLIC_PATH%xyz.
const publicUrl = '.';
//Get environment variables to inject into our app.
const env = getClientEnvironment(publicUrl);

//This is the development configuration.
//It is focused on developer experience and fast rebuilds.
//The production configuration is different and lives in a separate file.
module.exports = {
  //You may want 'eval' instead if you prefer to see the compiled output in DevTools.
  //See the discussion in https://github.com/facebookincubator/create-react-app/issues/343.
  devtool: 'cheap-module-source-map',
  //These are the "entry points" to our application.
  //This means they will be the "root" imports that are included in JS bundle.
  //The first two entry points enable "hot" CSS and auto-refreshes for JS.
  entry: [
    //We ship a few polyfills by default:
    require.resolve('./polyfills'),
    //Include an alternative client for WebpackDevServer. A client's job is to
    //connect to WebpackDevServer by a socket and get notified about changes.
    //When you save a file, the client will either apply hot updates (in case
    //of CSS changes), or refresh the page (in case of JS changes). When you
    //make a syntax error, this client will display a syntax error overlay.
    //Note: instead of the default WebpackDevServer client, we use a custom one
    //to bring better experience for Create React App users. You can replace
    //the line below with these two lines if you prefer the stock client:
    //require.resolve('webpack-dev-server/client') + '?/',
    //require.resolve('webpack/hot/dev-server'),
    require.resolve('react-dev-utils/webpackHotDevClient'),
    //Finally, this is your app's code:
    paths.appIndexJs,
    //We include the app code last so that if there is a runtime error during
    //initialization, it doesn't blow up the WebpackDevServer client, and
    //changing JS code would still trigger a refresh.
  ],
  output: {
    //Add /* filename */ comments to generated require()s in the output.
    pathinfo: true,
    //This does not produce a real file. It's just the virtual path that is
    //served by WebpackDevServer in development. This is the JS bundle
    //containing code from all our entry points, and the Webpack runtime.
    filename: 'static/js/bundle.js',
    //There are also additional JS chunk files if you use code splitting.
    chunkFilename: 'static/js/[name].chunk.js',
    //This is the URL that app is served from. We use "/" in development.
    publicPath: publicPath,
    //Point sourcemap entries to original disk location (format as URL on Windows)
    devtoolModuleFilenameTemplate: info =>
      path.resolve(info.absoluteResourcePath).replace(/\\/g, '/'),
  },
  resolve: {
    //This allows you to set a fallback for where Webpack should look for modules.
    //We placed these paths second because we want `node_modules` to "win"
    //if there are any conflicts. This matches Node resolution mechanism.
    //https://github.com/facebookincubator/create-react-app/issues/253
    modules: ['node_modules', paths.appNodeModules].concat(
      //It is guaranteed to exist because we tweak it in `env.js`
      process.env.NODE_PATH.split(path.delimiter).filter(Boolean)
    ),
    //These are the reasonable defaults supported by the Node ecosystem.
    //We also include JSX as a common component filename extension to support
    //some tools, although we do not recommend using it, see:
    //https://github.com/facebookincubator/create-react-app/issues/290
    //`web` extension prefixes have been added for better support
    //for React Native Web.
    extensions: ['.web.js', '.mjs', '.js', '.json', '.web.jsx', '.jsx'],
    alias: {

      //Support React Native Web
      //https://www.smashingmagazine.com/2016/08/a-glimpse-into-the-future-with-react-native-for-web/
      'react-native': 'react-native-web',
    },
  },
  module: {
    strictExportPresence: true,
    rules: [
      //TODO: Disable require.ensure as it's not a standard language feature.
      //We are waiting for https://github.com/facebookincubator/create-react-app/issues/2176.
      //{ parser: { requireEnsure: false } },

      //First, run the linter.
      //It's important to do this before Babel processes the JS.
      {
        test: /\.(js|jsx|mjs)$/,
        enforce: 'pre',
        use: [
          {
            options: {
              formatter: eslintFormatter,
              eslintPath: require.resolve('eslint'),

            },
            loader: require.resolve('eslint-loader'),
          },
        ],
        include: paths.appSrc,
      },
      {
        //"oneOf" will traverse all following loaders until one will
        //match the requirements. When no loader matches it will fall
        //back to the "file" loader at the end of the loader list.
        oneOf: [
          //"url" loader works like "file" loader except that it embeds assets
          //smaller than specified limit in bytes as data URLs to avoid requests.
          //A missing `test` is equivalent to a match.
          {
            test: [/\.bmp$/, /\.gif$/, /\.jpe?g$/, /\.png$/],
            loader: require.resolve('url-loader'),
            options: {
              limit: 10000,
              name: 'static/media/[name].[hash:8].[ext]',
            },
          },
          //Process JS with Babel.
          {
            test: /\.(js|jsx|mjs)$/,
            include: paths.appSrc,
            loader: require.resolve('babel-loader'),
            options: {

              //This is a feature of `babel-loader` for webpack (not Babel itself).
              //It enables caching results in ./node_modules/.cache/babel-loader/
              //directory for faster rebuilds.
              cacheDirectory: true,
            },
          },
          //"postcss" loader applies autoprefixer to our CSS.
          //"css" loader resolves paths in CSS and adds assets as dependencies.
          //"style" loader turns CSS into JS modules that inject <style> tags.
          //In production, we use a plugin to extract that CSS to a file, but
          //in development "style" loader enables hot editing of CSS.
          {
            test: /\.css$/,
            use: [
              require.resolve('style-loader'),
              {
                loader: require.resolve('css-loader'),
                options: {
                  importLoaders: 1,
                },
              },
              {
                loader: require.resolve('postcss-loader'),
                options: {
                  //Necessary for external CSS imports to work
                  //https://github.com/facebookincubator/create-react-app/issues/2677
                  ident: 'postcss',
                  plugins: () => [
                    require('postcss-flexbugs-fixes'),
                    autoprefixer({
                      browsers: [
                        '>1%',
                        'last 4 versions',
                        'Firefox ESR',
                        'not ie < 9', //React doesn't support IE8 anyway
                      ],
                      flexbox: 'no-2009',
                    }),
                  ],
                },
              },
            ],
          },
          //"file" loader makes sure those assets get served by WebpackDevServer.
          //When you `import` an asset, you get its (virtual) filename.
          //In production, they would get copied to the `build` folder.
          //This loader doesn't use a "test" so it will catch all modules
          //that fall through the other loaders.
          {
            //Exclude `js` files to keep "css" loader working as it injects
            //it's runtime that would otherwise processed through "file" loader.
            //Also exclude `html` and `json` extensions so they get processed
            //by webpacks internal loaders.
            exclude: [/\.js$/, /\.html$/, /\.json$/],
            loader: require.resolve('file-loader'),
            options: {
              name: 'static/media/[name].[hash:8].[ext]',
            },
          },
        ],
      },
      //** STOP ** Are you adding a new loader?
      //Make sure to add the new loader(s) before the "file" loader.
    ],
  },
  plugins: [
    //Makes some environment variables available in index.html.
    //The public URL is available as %PUBLIC_URL% in index.html, e.g.:
    //<link rel="shortcut icon" href="%PUBLIC_URL%/favicon.ico">
    //In development, this will be an empty string.
    new InterpolateHtmlPlugin(env.raw),
    //Generates an `index.html` file with the <script> injected.
    new HtmlWebpackPlugin({
      inject: true,
      template: paths.appHtml,
    }),
    //Add module names to factory functions so they appear in browser profiler.
    new webpack.NamedModulesPlugin(),
    //Makes some environment variables available to the JS code, for example:
    //if (process.env.NODE_ENV === 'development') { ... }. See `./env.js`.
    new webpack.DefinePlugin(env.stringified),
    //This is necessary to emit hot updates (currently CSS only):
    new webpack.HotModuleReplacementPlugin(),
    //Watcher doesn't work well if you mistype casing in a path so we use
    //a plugin that prints an error when you attempt to do this.
    //See https://github.com/facebookincubator/create-react-app/issues/240
    new CaseSensitivePathsPlugin(),
    //If you require a missing module and then `npm install` it, you still have
    //to restart the development server for Webpack to discover it. This plugin
    //makes the discovery automatic so you don't have to restart.
    //See https://github.com/facebookincubator/create-react-app/issues/186
    new WatchMissingNodeModulesPlugin(paths.appNodeModules),
  ],
  //Some libraries import Node modules but don't use them in the browser.
  //Tell Webpack to provide empty mocks for them so importing them works.
  node: {
    dgram: 'empty',
    fs: 'empty',
    net: 'empty',
    tls: 'empty',
    child_process: 'empty',
  },
  //Turn off performance hints during development because we don't do any
  //splitting or minification in interest of speed. These warnings become
  //cumbersome.
  performance: {
    hints: false,
  },
};
